Signal-seeking device



2 Sheets-Sheet 1 Filed May 25, 1955 Jan. 28, 1958 J. H. LOFTON 2,821,631

SIGNAL-SEEKING DEVICE Filed May 2:5, 1955 2 sheets-sheet 2 Fvg. 2.

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csp/4"" 46 INVENTOR. 75555 f7. LFTN limited States Patent O 8 Claims.(Cl. Z50- 40) Pa., assignor to Philco Pa., a corporation of Penn- Theinvention hereinafter described and claimed relates to signal receiversof the signal-seeking type which function, 1n response to successiveinitiations on the part of the user, to tune themselves automaticallyand successively to receivable signals within the reception range. Morepartlcularly, the invention has to do with signal receivers of. the typedescribed and claimed in the copending application of l. E. Laschenski,Serial No. 468,008, filed November 10, 1954, and assigned to theassignee of the present invention.

The apparatus of the aforesaid application provides for overallsignal-seeking operation i. e., signal-seeking operation whichprogresses through the entire reception range or band from one end ofthe band to the other. However, it also provides for limitedsignal-seeking operation over selected portions of the reception band.Thus, With respect to broadcasting stations to which the user of a radioreceiver customarily listens, it provides selection of signals in therespective portions of the reception band in which the transmittingfrequencies of such stations are located. By providing selective limitedsignal-seeking in response to selective operation of push-buttons, thetunlng operation is greatly simplified and elTort on the part of theoperator is minimized.

It is an object of the present invention to provide an improvedsignal-seeking receiver of the aforesaid type.

Another object of the invention is to provide improved apparatus forselectively limiting the predetermined portions of the reception rangeover which the signal-seeking operation is carried out.

A further object of the invention is to provide such an arrangement forlimited signal-seeking which is simple in construction, easy to adjust,and which is substantially immune to accidental change of setting of theelements which determine the selective limited signal-seeking portionsof the reception range.

In accordance with the present invention, there is provided in apparatusof the above-identified type, improved means whereby the limitedsignal-seeking portions of the broadcast range may be quickly and easilyselected or adjusted from one portion of the broadcast band to another.

The invention may be clearly understood from the following detaileddescription, with reference to the accompanying drawings wherein:

Figure 1 is a diagrammatic illustration of a signalseeking receiver inwhich the apparatus of the present invention is particularly adapted foruse;

Figure 2 is a sectional elevational view of apparatus embodying thepresent invention;

Figure 3 is a perspective View of one of the elements which determinethe selectable portions of the reception band for limited signalseeking;

Figure 4 is a sectional view taken on line 4--4 of Figure 2;

Figure 5 is a sectional view taken on line 5 5 of Figure 2; and

Figure 6 is a view similar to Figure 5 but showing a differentoperational condition.

It is believed that the present invention may best be understood byconsidering iirst the electrical system and the general operation of thereceiver, and then a mechanical structure incorporating the improvementafforded by the present invention.

The system which embodies the invention is preferably of the typedescribed and claimed in the above-mentioned Laschenski disclosure and,as shown in Figure l, includes a conventional signal receiver which, inthe embodiment depicted in the figure, is a superheterodyne radioreceiver. Such a receiver may comprise an antenna 11, one or more R. F.amplifier stages 12, a converter and oscillator stage 13, one or more I.F. amplifier stages 14, a detector 15, one or more audio amplifierstages 16, and a sound reproducer or loud-speaker 17. Tuning of thereceiver preferably is effected by movement of adjustable coresaccording to the well-known permeability tuning method, two such coresbeing represented at 18 and 19. The cores are moved by means of acarriage 20 to which they are connected as indicated by the dashed lines21 and 22. The carriage 20 preferably is actuated by means of anelectric motor 23 through suitable actuating means represented by theblock 24, and while other actuating means might be used for thispurpose, the apparatus shown and described in above-identitied copendingapplication is preferred.

While the invention is broadly applicable to signal receivers, it may beassumed that the radio receiver shown in Figure 1 is to be used on avehicle, such as an automobile, and therefore the usual vehicle batteryis represented at 25, and the usual vibrator and rectifier unit isrepresented in block form at 26. It will be understood that the battery25 and the unit 26 supply the operating voltages to the receivercomponents shown in block form. For simplicity, the connections forsupplying such voltages have been omitted.

The driving motor 23 is controlled by a relay 27 whose winding 28 isenergized from unit 26 by momentary closure of switch 29. The relaywinding 28 has one terminal connected to the anode of a control tube 30and the outer terminal connected to the positive high voltage supply ofthe rectifier unit 26. In addition, the terminal of winding 28 which isconnected to the anode of tube 30 is also connected through acurrent-limiting resistor to one terminal of single-pole single-throwswitch 29, the other terminal of which is connected to a point at groundpotential. When switch 29 is momentarily closed, relay 27 is energized,thereby connecting the cathode of control tube 30 to a point at groundpotential through relay contact 31. As a result, a heavy cathodeanodecurrent flows through control tube 30 and maintains energization ofrelay 27 independently of switch 29. Through its contact 32, the relayeffects energization of the motor 23 which is in circuit with thebattery 2S. Through contact 36, the relay mutes the radio receiver byshort-circuiting the input to the audio stages.

The motor 23 drives carriage 20 in a direction to tune the receiver tothe next receivable signal. When such a signal is tuned in, the tube 30is rendered non-conductive to deenergize the relay winding 28 thereby todeenergize the motor and to restore the operative condition of the audioinput, thereby producing audible signals which in the normal operationof the receiver serve to reproduce music or speech or the like and whichin accordance with this invention also indicate the moment for one ofthe manipulations in the station selecting operation. The opening ofrelay contact 31 opens the cathode circuit of tube 30 and thus rendersthe tube inoperative until such time as the relay is again energized byclosure of switch 29.

It iswell-known vinthe art to effect cut-od of a control tube inresponse to a tuned-in signal, and any of the known arrangements may beemployed to cut-off the control tube 30. Preferably, however, thecontrol arrangement is of the character disclosed and claimed in thecopending application of Ralph Bray, Serial No. 459,043, led September29, 1954, and is represented by the rectangle 33. In such a system, twosignals are derived from the I. F. portion of the receiver viaconductors 34 and 35 and are applied to a phase detector, the output ofwhich is coupled to the control grid of the control tube through adierentiating circuit.

As thus far described, the receiver comprises means for tuning insignals having frequencies within a predetermined frequency range, e. g.the broadcast band, and means for stopping the tuning operation when asignal is tuned in. In accordance with the present invention, and 1ncommon with the Laschenski contribution, provision is made for limitedsignal-seeking operation under control of at least two pairs ofswitches, one switch of each pair being actuated by the tuning means,and the other switch of each pair serving to render the rst switcheffective or ineffective. The stopping of the tuning operation is madeto depend, not only upon the reception of a signal, but also upon theconditioning of circuit means under control of the pairs of switches.

In the illustrated embodiment, there are tive switches numbered 39 to43, but it should be understood that this number of switch pairs isarbitrarily chosen. Each of the switches 39 to 43 forms a part of one ofsaid pairs of switches and comprises a movable contact 44 which isactuated by the carriage 20, as by apparatus indicated by the Vdashedlines 45 (see also Figure 2), and a stationary but adjustable contact46; the various adjustable contacts 46 being mounted for presetting soas to effect closure of the various switches 39 to 43 in differentportions of the operating range of the carriage corresponding todifferent portions of the reception band. In the illustrated system, thecontact 44 of each of the switches 39 to 43 is grounded, but this isonly because of the way in which the switches are made to serve thedesired vpurpose as hereinafter described. Associated with the switches39 to 43 are push-button switches 47 to 51 which are normally in thefront position, as shown, but are selectively movable to a backposition. Each of the push-button switches comprises a front Contact 52,a back contact 53, an intermediate contact 54, and a movable bridgingcontact 55 which engages the intermediate contact 54 in both positionsof the switch. The back contacts 53 of the push-button switches areconnected respectively to the stationary contacts 46 of the switches 39to 43. Actuation of any one of the push-buttton switches causes themovable contact element 55 to leave the front contact 52 and to engagethe back contact 53.

The above-described switches serve to effect selective limitedsignal-seeking through control of circuit means adapted to controloperation of the means for stopping the tuning operation. Preferablysuch circuit means 4is the cathode-to-ground connection for one or moreof the high frequency stages of the receiver. Thus, in the illustratedembodiment, the circuit conductor 56 is connected to the cathodes of thetubes in the R. F. and I. F. stages, and this conductor extends to thecontact 54 of the extreme left-hand push-button switch 47, which contactis a terminal to which ground potential must be applied as a conditionprecedent to the stoppage of the tuning operation. It will also be notedthat the front and intermediate contacts of adjacent push-buttonswitches are interconnected. It will be seen, therefore,

thatemovement of any one of the push-button switches tov its backposition will edect connection of the conductor 56 lto the correspondingone of switches 39 to 43.v As in' the case of the conventionalpush-button mechanism,

a latch bar 57 (see also Figure 2) serves to hold any one'- 4 of thepush-button switches in its back position, releasing any previouslyactuated switch.

Therefore, the conductor 56 can be connected to only one of the switches39 to 43 at one time, so that only one of said switches can be effectiveto apply ground potential to said conductor.

With the arrangement shown, if the push-button switches are all left intheir front positions, as shown, and switch 29 is actuated, the tuningsystem will operate to effect overall signal-seeking action from one endto the other of the reception band. This is due to the fact that theconductor 56 is connected to ground (through device 59) independently ofswitches 39 to 43 which are ineffective. However, actuation of any oneof the pushbutton switches 47 to 51 will cause the tuning system toeffect selective limited signal-seeking action over the selected portionof the reception band, because the conductor 56 will then be connectedto ground only as controlled by one of the switches 39 to 43.

To initiate overall signal-seeking operation of the system, the switchZ9 need only be closed momentarily. In the preferred embodimentillustrated, this switch is momentarily actuated by the latch bar 57which shifts momentarily toward the right, as in conventional pushbuttonarrangements, each time one of the push-buttons is depressed. Apush-button 5S, spring loaded at 95, is provided which serves simply toshift the latch bar momentarily to etect momentary closure of switch 29.

In signal-seeking receivers, it is generally desirable to provide fordecreased sensitivity of the receiver during overall signal-seekingoperation. The purpose of this is to insure that the tuning will bestopped only in response to a signal of adequate strength forsatisfactory operation of the receiver. Therefore, in the illustratedsystem, there is preferably provided `a sensitivity control device 59which may comprise a tapped resistor 60 and a multiposition switchhaving a grounded movable contact 61 and stationary contacts 62. Thisdevice is connected, as shown, to the front contact of push-buttonswitch 51 and to the normally-closed stationary contact 37 of relay 27.When the relay is deenergized, the device 59 is rendered ineffective asthe conductor 56 is connected to ground independently of the device 59through relay contact 37. However, when the relay 27 is energized, theground connection for conductor 56 through contact 37 is opened, and theconductor 56 is connected to ground through the switch arm 61. With thisswitch arm in its eXtreme lefthand position, the receiver sensitivity isnot reduced, but with the switch arm in other positions, the receiversensitivity is reduced according to the amount of included resistance.

The present invention is particularly concerned with the switchingmechanism providing improved selection of portions of the reception bandfor limited signal-seeking operation. In this regard, reference is nowmade to Figures 2 through 6.

In Figure 2 it is seen that the apparatus 45, which is indicated bydashed lines in Figure l, comprises an inverted channel member 62 towhich eXible contact lingers 44 are secured by clamping plate 63 andrivets 64. The push-button mechanism includes a front panel 65 securedto a base member 66. Above the base member isa horizontal shelf 67formed of insulating material and supported at its front on flange 68aof a shell 63 secured to front panel 65 by screws 69. At its rear, shelf67 is supported by a bracket 70 mounted on base plate 66. The member 62is moved by the carriage 20 (Fig. l) in a horizontal plane in the spacebetween base plate 66 and shelf 67 I(Fig. 2).

Secured to the underside of the insulating shelf 67 is a supportingbracket 71. While only one of these brackets is shown, it will ybeunderstood that each of the ve push-buttons 47 through 51, see Figure l,is so i provided. As shown in Figure 2,- each of these bracketssupports, as shown at 71a and 7llb, track means which in .5 thisembodiment of the invention comprises a rotatable shaft 72 which has aforwardly projecting stem 73 that projects through an aperture in thefront panel 65.

In particular accordance with the present invention, each of the shaftspreferably is I-shaped in cross-section, as shown in Figures 4 through6, with opposite at sides 74 and 75. It should be understood, however,that it is sufficient that only one flat side or reduced diameterportion be provided, as will appear more clearly as the descriptionproceeds.

Each of the shafts 72 passes through apertures 77 in end walls 78` ofone of the adjustable, stationary switch elements 46, which element maybe U-shaped, thus slidably to support the element upon the shaft, itbeing noted that this is the similarly designated switch elementmentioned in the preceding description in connection with Figure l. Eachof the end Walls 78 include an upper, reduced portion 78a (Fig. 5),which extends into an area between side llanges 76 of the associatedbracket 71, thus to prevent the element 46 from turning with thesupporting shaft 72. The central area 79 of the bottom surface of eachelement 46 is framed by an insulating member 80 (see Figure 3) which isheld against the bottom surface of element 46 by turned-down lugs 81thereon. The framed portion of the bottom surface of the contact element46 is adapted to be engaged by one of the resilient contact fingers 44whose free end portion wipes over said area between the retaining lugs81 during signal-seeking action.

As shown in Figures 2 and 5, each of elements 46 may be locked againstslidable movement on shaft 72 by resilient means comprising leaf spring82 bearing upwardly against the bottom of the shaft when the latter isin a vertically disposed position with the reduced diameter portionturned away from the spring. Reduced end portions 83 of the springextend through slots 84 formed in member 46 at the juncture of the endwalls 73 with the bottom surface 8S. By rotating shaft 72 through 90 sothat the reduced diameter portion faces spring 82, as shown in Figure 6,the spring tension is released and element 46 is free to slide on theshaft.

As may be seen in Figure 2, each of the shaft-supporting brackets 71 hasan upwardly-extending contact linger 53, which corresponds to thesimilarly designated contact in Figure l and is an element of thecorresponding pushbutton switch. Thus this finger is electricallyconnected to contact element 46 through the shaft and associatedbracket. This linger 53 projects upwardly through an aperture (notshown) in the insulating shelf 67 so that it is within the enclosuredefined by the shelf 67 and the previously mentioned shell 68. Thisenclosure also contains the other elements of the push-button switches47 to 51. As shown in Figure 2, each of these switches comprises a slidebar 86 which is urged forwardly to the right, by a spring 87. Each slidebar carries an insulating plate 88 on which contact element 55 ismounted, the latter being the similarly designated contact of Figure l.This contact is a bridging contact which normally engages the front andintermediate contacts 52 and 54 which are mounted on the insulatingshelf 67. The electrical connections to the latter contacts are as shownin Figure l. Normally, the bridging contact 55 engages contacts 52 and54, but when the slide bar 86 is actuated, the bridging contact 55leaves contact 52 and engages the back contact 53 so that it thenbridges the contacts 53 and 54. Upon such actuation of any push button,this push button is latched behind bar 57 by cam and shoulder 91, 92,whereas during such actuation all other push buttons are unlatched, asis well known to the art.

As previously described in connection with Figure l, the contactelements 46, in cooperation with contact lingers 44, serve to deneportions of the signal reception range or band for limitedsignal-seeking tuning. The contact elements 46 may be preset forselection of a 6 particular broadcasting station in the novel manner nowto be described.

With all of the push-buttons in their outer position (Figure l) andshafts 72 all turned to the position shown in Figure 6, the Search unitis operated through one cycle, preferably with the sensitivity adjustedtoo low to pick up a signal suiciently strong to stop the operation.During the complete cycle, spring contacts 44 pick up elements 46 bymovement of the ends 44a of the contacts into the framed central areas79. Elements 46 then move freely on shafts 72, and as a unit with member45 and contacts 44, during cycling of the core bar.

The sensitivity control 59 is then adjusted to stop tuning in responseto a signal of desired strength, and when the search unit has beenstarted again and the first such response received any one of the shafts72, depending upon the push-button with which it is desired to associatethis signal, is turned as shown in Figure 5, thus locking the selectedelement 46 on the shaft in the position automatically established by thestopping of the tuning operation. The same procedure is followed insetting up the other push-buttons to receive other signals. As pointedout below, this is a simple and very accurate pre-sele-ction procedure.

With this arrangement, it is unnecessary to make highly accurateadjustments for preselecting stations to be tuned in by thepush-buttons. The signal-seeking action within the available range initself effects accurate automatic positioning of a switch element 46, asdescribed above; and the manual fixing of this element, in the positionautomatically established by the apparatus described, avoids any dangerof disturbing said position, thereby insuring highly accurate subsequenttuning of the receiver to the desired station. This eliminates the needfor extremely accurate mechanical tolerances and adjustments.Furthermore, the presetting adjustment is simple and can easily beperformed by the user.

What is claimed is:

1. In switching apparatus wherein a first contact element can be movedin predetermined directions by a power means, relative to a second,normally stationary Contact element which is adjustable in saiddirections, an adjustment selector for the second element, comprising:track means for the adjustable contact element, extending parallel tosaid directions; means for inter-engaging and disengaging the first andsecond contact elements so that the power means may effect movement ofthe inter-engaged elements, along the track means; means for stoppingsuch movement; and engagement control means, operable after suchstopping to move the track means and a part of the adjustable contactelement relative to one another, transversely of the track means, andfor thereby fixing the adjustable contact element in the positionestablished by said stopping.

2. In apparatus as claimed in claim 1, engagement control means asdescribed including means for manually moving only the track meanstransversely of its length.

3. In apparatus as claimed in claim 2, track means comprising aflattened shaft rockably engageable with the adjustable contact element.

4. In a signal receiver, a set of tuning elements; motoractuated meansfor moving such elements relative to one another into a position wherethey are tuned to a preselected signal; switch means adapted to stopsaid motor actuated means exactly in the tuned position, said switchmeans comprising a contact normally movable by said motor-actuated meansand an adjustable, normally xed Contact; and adjustment means for thelatter contact, comprising means for mechanically inter-engaging saidnormally fixed and movable contacts for joint movement, in order toadjust the adjustable contact, and engagement control means fixing theadjustable contact pursuant to and exactly at a point of said stopping,to correspondingly preselect a different signal.

5. In a receiver as claimed in claim 4, engagement` control means asdescribed including track meansV for the adjustable contact; means onthe adjustable contact for gripping the track means in a rst position ofthe track means and for substantially releasing it in a second positionthereof; and means for placing the track means in either of saidpositions.

6. In a receiver as claimed in claim 5, engagement control means asdescribed including resilient means on the adjustable contact forengaging and disengaging the track means.

7. In a receiver as claimed in claim 5, the feature that the trackmeans, in moving from one of said positions to the other, movestransversely of the movement of said elements.

8. In a receiver as claimed in claim 5, means for'interengaging asdescribed, including a resilient contactor linger on one of thecontacts.

References Cited in the le of this patent UNITED STATES PATENTS1,906,106 Schaefer Apr. 25, 1933 2,034,254 Stenerson Mar. 17, 19362,177,850 Vogt et al Oct. 31, 1939 2,186,828 Forstrorn Ian. 9, 19402,501,003 Pifer Mar. 21, 1950

